Field of the Invention
The invention lies in the automotive technology field. More specifically, the invention relates to a method and a control configuration for controlling the drive train of a motor vehicle. Such a drive train controller includes, on the one hand, an engine and an engine controller by means of which variables which influence the engine torque, for example the ignition timing and the metering of fuel to the cylinders, are controlled. On the other hand, it also includes an automatic transmission and a transmission controller by means of which shifting operations of the automatic transmission are controlled.
In prior art transmission controllers for motor vehicles, the transmission ratio of the transmission is set automatically in dependence on the position of the gas pedal and of the driving velocity by reference to stored characteristic diagrams. Instead of the position of the gas pedal in the narrower sense, it is also possible to use the signal of a so-called electronic accelerator pedal (E-Gas) or a different variable derived from the engine torque which the driver requests. In this context, various driving parameters and operating conditions of the motor vehicle are taken into account. See, for example, U.S. Pat. No. 5,957,990 (international publication WO 97/01051). The gear speed which is to be respectively engaged or--in the case of infinitely variable transmissions--the transmission ratio which is to be set is selected by control switching operations which operate, for example, using the methods of fuzzy logic. With this logic, the knowledge of experts which has been acquired through experience is described in the form of a so-called rule base and is thus used for the closed-loop or open-loop control operations of the motor vehicle transmission. The logic circuit generates control signals with which, inter alia, the transmission ratio of the transmission is defined.
A prior art integrated drive train controller for a motor vehicle interprets the position of the gas pedal and the brake pedal as a wheel torque which is required by the driver. See U.S. Pat. No. (Ser. No. 08/937,253) and German published patent application DE 196 37 210 A1. It has a calculation device by means of which the positions of the gas pedal and of the brake pedal are received and from which central control parameters for the drive sources and the decelerating units of the drive train are generated.
It is known to generate the setpoint braking torques intended for the drive wheels of a vehicle by means of engine braking torques and operating braking torques. See U.S. Pat. No. 5,613,743 and German published patent application DE 42 30 101 A1.
Furthermore, U.S. Pat. No. 5,514,050 (German published patent application DE 43 30 391 A1) discloses a method for controlling a drive train of a motor vehicle in which a brake signal that is triggered by the driver by activating the brake pedal generates an engine braking torque as a function of the braking effect by shifting down the automatic transmission. The engine braking torque can be metered here either constantly or variably in accordance with a characteristic curve.
There exist driving situations in which an activation of the brakes by the driver should expediently be supported by the drive train of the motor vehicle.